Conventionally, in testing semiconductors for evaluation, and more particularly in a reliability evaluation test, EM (electromigration) has been an important test element for evaluating reliability such as life of a semiconductor.
An EM evaluation observes how the electrons flowing through thin wires formed in a semiconductor element push the metal ions toward the positive potential, and how the resulting increase in current density at the holes causes wire breakage. Furthermore, in order to save time, an EM evaluation test is carried out by increasing a current flow through the semiconductor element under high temperatures (200° C. to 400° C.) where metal ions are activated, and changes in wiring resistance over time are measured for evaluation.
Thus, since an EM evaluation is conducted under high temperatures, the semiconductor is generally assembled by die bonding to an expensive heat-resistant ceramic package and then making bonding wires for every evaluation element (TEG: test element group).
The complete package is mounted in an even more expensive ceramic socket, is drawn out of the high temperature with a special heat-resistant electric wire, and is wired to a connector connected to a measuring instrument. In this method, a great deal of time and cost are required for packaging, and the prices of evaluation devices including the sockets and the like become high.
Accordingly, there have been proposed semiconductor evaluation methods which do not employ packaging steps or wiring using a socket or a heat-resistant wire, but directly connect a TEG in a wafer state to a wiring circuit on a wiring substrate, as disclosed in, for example, Japanese Laid-Open Publication No. 45740/1997 (Tokukaihei 9-45740; published on Feb. 14, 1997) (Document 1), and Japanese Laid-Open Publication No. 329759/2002 (Tokukai 2002-329759; published on Nov. 15, 2002) (Document 2).
However, in Document 1, an evaluation is only conducted to check the operative condition of a semiconductor chip at ordinary temperature, and it is not for conducting an EM evaluation on a semiconductor element under high temperatures.
On the contrary, Document 2 is for conducting an EM evaluation and the like on a semiconductor element under high temperatures. However, the method suffers from a drawback in that, when a semiconductor wafer and a measuring instrument, connected to each other through a prober, are heated to a high temperature (400° C.), the heat will cause trouble in the prober, and an accurate evaluation cannot be carried out.
The prober may be processed to withstand heat; however, this will increase the cost of an entire evaluation device.